There are many different types of scoliosis. Scoliosis is classified according to its cause and the time it was diagnosed. The most common form of scoliosis is adolescent idiopathic scoliosis, which is a case of scoliosis with no obvious cause that was diagnosed in adolescence.
Since most types of scoliosis are termed idiopathic, it is important to understand what this word means. Idiopathic is the term doctors use to describe a disease that has no obvious cause. It does not mean that there is no cause, or that the cause is genetic; it simply means that there isn’t one specific factor that caused the scoliosis to develop. Since most researchers believe scoliosis is a multifactorial disease with many different potential aspects that influence its development and progression, it makes sense that most types of scoliosis would be called idiopathic.
When scoliosis results from a defect in the spine that was present at birth, it is called congenital. Other types of scoliosis arise from diseases such as cerebral palsy (neuromuscular scoliosis) or accidents (traumatic scoliosis).
Scoliosis that is diagnosed in a child younger than 3 is called infantile scoliosis; many times (but not always), these cases are caused by improper growth of one of the bones of the spine (a hemivertebra). Juvenile scoliosis is diagnosed between the ages of 3 and 10. These cases tend to be more worrisome than adolescent cases because the spine has so much more growing left to do. Scoliosis that arises in adulthood, either due to trauma or degeneration of the spinal discs (adult degenerative (or de novo) scoliosis), is different from adult idiopathic scoliosis, which is essentially a person with juvenile or adolescent idiopathic scoliosis who has grown up.
Scoliosis is sometimes described as mild, moderate, or severe, although it should be noted that these are not formal classifications. Mild scoliosis generally is used to refer to cases where the Cobb angle is 20 degrees or less, and watching & waiting, or perhaps exercises, are traditionally recommended. Moderate scoliosis ranges between 20 and 40 degrees, and it is at this stage that bracing is typically recommended for an adolescent. Severe scoliosis is often used to refer to cases that are typically around 40 degrees in an adolescent or 45 degrees in an adult, and have reached the level where an orthopedic surgeon would recommend surgery.